Before every operation, the POST program records its code into a special diagnostic port. And if the reason of the system malfunction could not be found from audible tones or messages on a display, you may try to find the POST-code of the error and decode it.

You may identify the POST-code when the error occurs in one of the following ways:

  • Some models of motherboards have built-in indicator of POST-codes. Such indicators could be found in EPoX boards, some models of ABIT and other manufacturers.
  • When the system is booting, the POST-codes may be displayed in the corner of the screen. But this method does not allow diagnosing errors before the video adapter is launched.
  • If your motherboard has not any built-in tools for the POST-codes displaying, it is necessary to use a special POST-board which is inserted into PCI slot.

To decode the POST-codes, you have to find the table with POST-codes for your version of BIOS. It can sometimes be found in the board manual. Otherwise, it can be found on a site of BIOS manufacturer.